Fabrication and photoluminescence properties of erbium doped size-controlled silicon nanocrystals

Er doping of dense arrays of nearly monodisperse Si nanocrystals produced by a new SiO/SiO2 superlattice approach is presented. This synthesis method is fully compatible with standard Si technology. The prepared samples show a strong increase of Er-related luminescence by a factor of up to 5000 in comparison with Er-doped bulk SiO2. Photoluminescence (PL) spectra and transients of the undoped and Er-doped size-controlled nanocrystalline Si/SiO2 superlattices have been comparatively investigated as a function of implantation dose and Si nanocrystal size. It is shown that the energy of the optically excited Si nanocrystals can almost be completely transferred to the Er3+ ions, resulting in a very strong emission at 1.54 μm. The efficiency of the energy transfer increases for smaller crystal sizes and an increasing overlap between the emission energy of the Si-related luminescence and the absorbing Er3+ energy levels. For superlattices with nanocrystal sizes of 2 nm a transfer efficiency to the Er3+ ions is found to be nearly one at room temperature under an excitation with photons of 3.7 eV. This properties of a highly efficient excitation of the Er ions via the Si nanocrystals is in agreement with the Förster mechanism.